EP1320559B1 - Method for preactivating catalysts - Google Patents

Abstract

Catalysts for the polymerization of C2-C20-olefins are preactivated by a process in which the catalyst is first mixed with the respective monomer, then, if appropriate, the respective cocatalyst is added and the resulting mixture is subsequently subjected to preactivation in a tube reactor and the catalyst which has been preactivated in this way is finally introduced into the actual polymerization reactor, wherein the mixture of catalyst, any cocatalyst and monomer is passed through the tube reactor in turbulent plug flow at a Reynolds number of at least 2 300.

Description

The present invention relates to a process for the pre-activation of catalysts for the polymerization of C ₂ -C ₂₀ olefins, wherein first the catalyst is mixed with the respective monomer, then optionally the respective cocatalyst added and the resulting mixture subsequently ßend in a tubular reactor of a Preactivation subjects and finally introduces the thus pre-activated catalyst in the actual polymerization, characterized in that the mixture of catalyst, optionally cocatalyst and monomer in the form of a turbulent plug flow having a Reynolds number of at least 2300 is passed through the tubular reactor.

Polymers of C ₂ -C ₁₀ olefins can be prepared by both liquid phase polymerization and by slurry polymerization or gas phase polymerization. Since the resulting solid polymer can be easily separated from the gaseous reaction mixture, polymerizing out increasingly from the gas phase. The polymerization is carried out with the aid of a Ziegler-Natta catalyst system, which usually consists of a titanium-containing solid component, an organic aluminum compound and an organic silane compound ( EP-B 45 977 . EP-A 171 200 . US Pat. No. 4,857,613 . US Pat. No. 5,288,824 ).

The polymers of C ₂ -C ₁₀ -olefins include the corresponding homopolymers, copolymers and so-called block or impact copolymers. The latter are usually mixtures of various homopolymers or copolymers of C ₂ -C ₁₀ -alk-1-enes, which are distinguished, above all, by good impact strength. They are usually prepared in so-called reactor cascades of at least two reactors connected in series and often in at least a two-stage process, wherein the polymer obtained in a first reactor is transferred in the presence of still active Ziegler-Natta catalyst components in a second reactor in which additional monomers are polymerized.

If catalysts having a high productivity are used in the preparation of polymers of C ₂ -C ₂₀ olefins, problems are observed in particular in large-scale plants with regard to the morphology of the polymer obtained, in particular with regard to an increased proportion of fine constituents and with regard to the formation of chunks in the reactor , Furthermore, productivity is often lowered in such large-scale plants compared with smaller plants. Such problems can be solved, inter alia, by subjecting the polymerization catalyst to a pre-polymerization under mild conditions before it is fed into the actual polymerization reactor. Such prepolymerization can be carried out either in a batch reactor or in a continuous stirred reactor ( WO 97/33920 ). Furthermore, it is possible to run the prepolymerization continuously in a loop reactor ( WO 95/22565 . EP-A 57,4821 . EP-A 560312 . WO 98/55519 ). In a pre-polymerization in a loop reactor, there are often problems regarding the storage and productivity of the prepolymerized catalyst.

From the WO 97/33920 It is known to solve the difficulties encountered in the prepolymerization in that they are carried out in a very long tubular reactor. However, such a long tube reactor is not suitable for high productivity with long reactor run times, since such a tube reactor is difficult to control and you can not turn off the risk that the reactor is clogged. After the apprenticeship of EP-A 279 153 For example, the clogging of a tubular reactor used for prepolymerization can be significantly reduced by reducing the average residence time in the tubular reactor to less than 1 minute.

The present invention therefore an object of the invention to remedy the disadvantages and to develop a new process for the pre-activation of catalysts for the polymerization of C ₂ -C ₂₀ olefins, which is characterized, inter alia, by increased productivity and process stability over the longest possible period and leads to polymers with an improved morphology.

Accordingly, a novel process for the pre-activation of catalysts for the polymerization of C ₂ -C ₂₀ olefins was found, wherein first the catalyst is mixed with the respective monomer, then optionally the respective cocatalyst added and then subjecting the resulting mixture in a tubular reactor to a pre-activation and finally the in this way preactivated catalyst is introduced into the actual polymerization reactor, which is characterized in that the mixture of catalyst, optionally cocatalyst and monomer in the form of a turbulent plug flow having a Reynolds number of at least 2300 is passed through the reactor.

As C ₂ -C ₂₀ -olefins in the process according to the invention, in particular C ₂ -C ₂₀ -alk-1-enes, such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, hept-1 -en or oct-1-en, with ethylene, propylene or but-1-en are preferably used. Furthermore, under the name C ₂ -C ₂₀ olefins, in particular also internal C ₄ -C ₂₀ -olefins such as but-2-ene or isoprene, C ₄ -C ₂₀ -dienes such as 1,4-butadiene, 1.5 Hexadiene, 1,9-decadiene, 5-ethylidene-2-norbornene, 5-methylidene-2-norbornene, furthermore cyclic olefins such as, for example, norbornene or α-pinene or else trienes, for example 1,6-diphenyl-1,3, 5-hexatriene, 1,6-di-tert-butyl-1,3,5-hexatriene, 1,5,9-cyclododecatriene, trans, trans-farnesol, as well as polyunsaturated fatty acids or fatty acid esters. The process is suitable for the preparation of homopolymers of C ₂ -C ₂₀ -olefins or copolymers of C ₂ -C ₂₀ -olefins, preferably with up to 30 wt .-% of copolymerized other olefins having up to 20 carbon atoms, into consideration. Copolymers are to be understood here as meaning both random copolymers and the so-called block or impact copolymers.

In general, the inventive method for pre-activation of catalysts in the polymerization in at least one reaction zone, often in two or more reaction zones is carried out, i. the polymerization conditions differ so far in the reaction zones that polymers having different properties are produced. For example, for the homopolymers or random copolymers this may be the molecular weight, i. to widen the molecular weight distribution, polymers having different molecular weights are produced in the reaction zones. Preferably, different monomers or monomer compositions are polymerized in the reaction zones. This then usually leads to the block or Impactcopolymerisaten.

The process according to the invention is particularly suitable for the preparation of homopolymers of propylene or of copolymers of propylene with up to 30% by weight of copolymerized other olefins having up to 10 carbon atoms. The copolymers of propylene are in this case random copolymers or block or Impactcopolymerisate. If the copolymers of propylene are built up statistically, they generally contain up to 15 wt .-%, preferably up to 6 wt .-%, other olefins having up to 10 C-atoms, in particular ethylene, but-1-ene or a mixture of ethylene and But -1-en.

The block or impact copolymers of propylene are polymers in which in the first stage a propylene homopolymer or a random copolymer of propylene with up to 15 wt .-%, preferably up to 6 wt .-%, of other olefins with up to 10 C. -Atomen and then in the second stage, a propylene-ethylene copolymer having ethylene contents of 15 to 99 wt .-%, wherein the propylene-ethylene copolymer may additionally contain further C ₄ -C ₁₀ olefins, polymerized. As a rule, so much of the propylene-ethylene copolymer is polymerized that the copolymer produced in the second stage in the final product has a content of 3 to 90 wt .-%.

As catalysts to be used, i.a. Philips catalysts based on chromium compounds or Ziegler catalysts are used. The polymerization can i.a. also be carried out by means of a Ziegler-Natta catalyst system. Particular preference is given to using those catalyst systems which, in addition to a titanium-containing solid component a), also have cocatalysts in the form of organic aluminum compounds b) and electron donor compounds c).

In the process according to the invention, however, it is also possible to use Ziegler-Natta catalyst systems based on metallocene compounds or on the basis of polymerization-active metal complexes as catalysts.

For the preparation of the titanium-containing solid component a), the halides or alcoholates of tri- or tetravalent titanium are generally used as the titanium compounds, although titanium alkoxyhalogen compounds or mixtures of different titanium compounds are also suitable. The titanium compounds which contain chlorine as the halogen are preferably used. Also preferred are the titanium halides, which contain only halogen in addition to titanium, and in particular the titanium chlorides and in particular titanium tetrachloride.

The titanium-containing solid component a) preferably contains at least one halogen-containing magnesium compound. Halogens are understood to mean chlorine, bromine, iodine or fluorine, with bromine or, in particular, chlorine being preferred. The halogen-containing magnesium compounds are either used directly in the preparation of the titanium-containing solid component a) or at their production formed. Suitable magnesium compounds which are suitable for the preparation of the titanium-containing solid component a) are, in particular, the magnesium halides, in particular magnesium dichloride or magnesium dibromide, or magnesium compounds from which the halides can be obtained in a customary manner, for example by reaction with halogenating agents, such as magnesium alkyls. Magnesium aryls, magnesium alkoxy or magnesium aryloxy compounds or Grignard compounds are suitable. Preferred examples of halogen-free compounds of magnesium which are suitable for the preparation of the titanium-containing solid component a) are n-butylethylmagnesium or n-butyloctylmagnesium. Preferred halogenating agents are chlorine or hydrogen chloride. However, the titanium halides can also serve as halogenating agents.

In addition, the titanium-containing solid component a) expediently contains electron donor compounds, for example monofunctional or polyfunctional carboxylic acids, carboxylic anhydrides or carboxylic acid esters, furthermore ketones, ethers, alcohols, lactones or phosphorus or organosilicon compounds.

verwendet, wobei X und Y jeweils für ein Chlor- oder Bromatom oder einen C₁-C₁₀-Alkoxyrest oder gemeinsam für Sauerstoff in Anhydridfunktion stehen. Besonders bevorzugte Elektronendonorverbindungen sind Phthalsäureester, wobei X und Y einen C₁-C₈-Alkoxyrest bedeuten. Beispiele für vorzugsweise eingesetzte Phthalsäureester sind Diethylphthalat, Di-n-butylphthalat, Di-isobutylphthalat, Di-n-pentylphthalat; Di-n-hexylphthalat, Di-n-heptylphthalat, Di-n-octylphthalat oder Di-2-ethylhexylphthalat.Preferred electron donor compounds within the titanium-containing solid component are carboxylic acid derivatives and in particular phthalic acid derivatives of the general formula (II)

where X and Y are each a chlorine or bromine atom or a C ₁ -C ₁₀ alkoxy radical or together are oxygen in the anhydride function. Particularly preferred electron donor compounds are phthalic acid esters, where X and Y denote a C ₁ -C ₈ alkoxy radical. Examples of preferably used phthalic acid esters are diethyl phthalate, di-n-butyl phthalate, di-isobutyl phthalate, di-n-pentyl phthalate; Di-n-hexyl phthalate, di-n-heptyl phthalate, di-n-octyl phthalate or di-2-ethylhexyl phthalate.

Further preferred electron donor compounds within the titanium-containing solid component are diesters of 3- or 4-membered, optionally substituted cycloalkyl-1,2-dicarboxylic acids, as well as monoesters of substituted benzophenone-2-carboxylic acids or substituted benzophenone-2-carboxylic acids. As hydroxy compounds, the alkanols customary in esterification reactions are used in these esters, for example C ₁ -C ₁₅ -alkanols or C ₅ -C ₇ -cycloalkanols, which in turn can carry one or more C ₁ -C ₁₀ -alkyl groups, furthermore C ₆ -C ₁₀ -phenols.

It is also possible to use mixtures of different electron donor compounds.

In the preparation of the titanium-containing solid component a), usually from 0.05 to 2.0 mol, preferably from 0.2 to 1.0 mol, of the electron donor compounds are used per mole of the magnesium compound.

In addition, the titanium-containing solid component a) may contain inorganic oxides as a carrier. As a rule, a finely divided inorganic oxide is used as the carrier, which has an average particle diameter of from 5 to 200 μm, preferably from 20 to 70 μm. The mean particle diameter here is to be understood as meaning the volume-related mean value (median value) of the particle size distribution determined by Coulter Counter Analysis.

The grains of the finely divided inorganic oxide are preferably composed of primary particles which have an average particle diameter of the primary particles of from 1 to 20 μm, in particular from 1 to 5 μm. The so-called primary particles are porous, granular oxide particles, which are generally obtained by grinding from a hydrogel of the inorganic oxide. It is also possible to screen the primary particles before further processing.

Furthermore, the preferred inorganic oxide to be used is also characterized in that it has cavities or channels with an average diameter of 0.1 to 20 .mu.m, in particular from 1 to 15 .mu.m, whose macroscopic volume fraction of the total particle in the range of 5 to 30 %, in particular in the range of 10 to 30%.

The determination of the average particle diameter of the primary particles and of the macroscopic volume fraction of the cavities and channels of the inorganic oxide is expediently carried out by image analysis with the aid of scanning electron microscopy or electron probe microanalysis at grain surfaces and at grain cross sections of the inorganic oxide. The obtained images are evaluated and determined therefrom, the average particle diameter of the primary particles and the macroscopic volume fraction of the cavities and channels. The image analysis is preferably carried out by transfer of the electron microscopic Data in a gray value binary image and the digital evaluation by means of a suitable computer program, such as the software package Analysis of Fa. SIS.

The inorganic oxide to be preferably used can be obtained, for example, by spray-drying the ground hydrogel mixed therewith with water or an aliphatic alcohol. Such finely divided inorganic oxides are also commercially available.

The finely divided inorganic oxide further usually has a pore volume of 0.1 to 10 cm ³ / g, preferably from 1, 0 to 4.0 cm ³ / g, and a specific surface area of 10 to 1000 m ² / g, preferably of 100 to 500 m ² / g, on, which are to be understood by mercury porosimetry according to DIN 66133 and by nitrogen adsorption according to DIN 66131 values.

It is also possible to use an inorganic oxide whose pH, i. the negative decadic logarithm of the proton concentration is in the range of 1 to 6.5 and especially in the range of 2 to 6.

Suitable inorganic oxides are, in particular, the oxides of silicon, aluminum, titanium or one of the metals of the I or II main group of the Periodic Table. As a particularly preferred oxide in addition to alumina or magnesium oxide or a layered silicate especially silica (silica gel) is used. It is also possible to use mixed oxides such as aluminum silicates or magnesium silicates.

The inorganic oxides used as carriers contain water on their surface. This water is partly physically bound by adsorption and partly chemically in the form of hydroxyl groups. By thermal or chemical treatment, the water content of the inorganic oxide can be reduced or completely eliminated, which are usually used in a chemical treatment conventional drying agents such as SiCl ₄ , chlorosilanes or aluminum alkyls. The water content of suitable inorganic oxides is from 0 to 6% by weight. Preferably, an inorganic oxide in the form as commercially available is used without further treatment.

The magnesium compound and the inorganic oxide are present within the titanium-containing solid component a) preferably in such amounts that per mole of the inorganic oxide of 0.1 to 1.0 mol, in particular from 0.2 to 0.5 mol of the compound of magnesium are present.

1. a) kommen in der Regel ferner C₁- bis C₈-Alkanole wie Methanol, Ethanol, n-Propanol, Isopropanol, n-Butanol, sek.-Butanol, tert.-Butanol, Isobutanol, n-Hexanol, n-Heptanol, n-Oktanol oder 2-Ethylhexanol oder deren Mischungen zum Einsatz. Bevorzugt wird Ethanol verwendet.

In the preparation of the titanium-containing solid component

1. a) C ₁ to C ₈ alkanols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, isobutanol, n-hexanol, n-heptanol, are generally also present. n-octanol or 2-ethylhexanol or mixtures thereof are used. Preferably, ethanol is used.

The titanium-containing solid component can be prepared by methods known per se. Examples are among others in the EP-A 45 975 , of the EP-A 45 977 , of the EP-A 86 473 , of the EP-A 171 200 , of the GB-A 2 111 066 , of the US Pat. No. 4,857,613 and the US Pat. No. 5,288,824 described. This is preferred from the DE-A 195 29 240 known method applied.

Suitable aluminum compounds b) are, in addition to trialkylaluminum, also those compounds in which an alkyl group is replaced by an alkoxy group or by a halogen atom, for example by chlorine or bromine. The alkyl groups may be the same or different. Linear or branched alkyl groups are suitable. Preference is given to using trialkylaluminum compounds whose alkyl groups each have 1 to 8 C atoms, for example trimethylaluminum, triethylaluminum, triisobutylaluminum, trioctylaluminum or methyldiethylaluminum or mixtures thereof.

In addition to the aluminum compound b) is usually used as a further cocatalyst electron donor c) such as mono- or polyfunctional carboxylic acids, carboxylic anhydrides or carboxylic acid esters, ketones, ethers, alcohols, lactones, and organophosphorus and organosilicon compounds, the electron donor c) the same or may be different from the electron donor compounds used for the preparation of the titanium-containing solid component a). Preferred electron donor compounds are organosilicon compounds of the general formula (I)

R ¹ _n Si (OR ² ) _4-n (I)

wherein R ^{1 is the} same or different and is a C ₁ -C ₂₀ alkyl group, a 5- to 7-membered cycloalkyl group which in turn may be substituted by C ₁ -C ₁₀ alkyl, a C ₆ -C ₁₈ aryl group or a C ₆ -C ₁₈ -aryl-C ₁ -C ₁₀ -alkyl group, R ^{2 is} identical or different and denotes a C ₁ -C ₂₀ -alkyl group and n is the integer 1, 2 or 3. Particularly preferred are those Compounds in which R ¹ is a C ₁ -C ₈ alkyl group or a 5- to 7-membered cycloalkyl group, and R ² represents a C ₁ -C ₄ alkyl group, and n represents the numbers 1 or 2.

Among these compounds, dimethoxydiisopropylsilane, dimethoxyisobutylisopropylsilane, dimethoxydiisobutylsilane, dimethoxydicyclopentylsilane, dimethoxyisopropyl-tert-butylsilane, dimethoxyisobutyl-sec-butylsilane and dimethoxyisopropyl-sec-butylsilane are particularly noteworthy.

The cocatalysts b) and c) are preferably used in an amount such that the atomic ratio between aluminum from the aluminum compound b) and titanium from the titanium-containing solid component a) is from 10: 1 to 800: 1, in particular from 20: 1 to 200: 1 and the molar ratio between the aluminum compound b) and the electron donor compound c) is from 1: 1 to 250: 1, especially from 10: 1 to 80: 1.

The titanium-containing solid component a), the aluminum compound b) and the electron donor compound c) generally used together form the Ziegler-Natta catalyst system. The catalyst components b) and c) can be introduced individually into the tubular reactor together with the titanium-containing solid component a) or as a mixture or else in any desired order, where they are subjected to preactivation.

In the process according to the invention, it is also possible to use Ziegler-Natta catalyst systems based on metallocene compounds or on the basis of polymerization-active metal complexes.

Metallocenes are here understood to mean complex compounds of metals of subgroups of the periodic table with organic ligands which, together with metallocenium ion-forming compounds, give effective catalyst systems. For use in the process according to the invention, the metallocene complexes are usually supported in the catalyst system. The carriers used are often inorganic oxides. Preference is given to the inorganic oxides described above, which are also used to prepare the titanium-containing solid component a).

Commonly used metallocenes contain as central atoms titanium, zirconium or hafnium, with zirconium being preferred. In general, the central atom is bonded via a π bond to at least one, generally substituted, cyclopentadienyl group and to further substituents. The other substituents can Halogens, hydrogen or organic radicals, with fluorine, chlorine, bromine or iodine or a C ₁ -C ₁₀ alkyl group are preferred.

Preferred metallocenes contain central atoms which are bonded via two π bonds to two substituted cyclopentadienyl groups, with particular preference being given to those in which substituents of the cyclopentadienyl groups are bonded to both cyclopentadienyl groups. In particular, complexes are preferred whose cyclopentadienyl groups are additionally substituted by cyclic groups on two adjacent C atoms.

Preferred metallocenes are also those which contain only one cyclopentadienyl group but which is substituted by a radical which is also bonded to the central atom.

Suitable metallocene compounds are, for example
Ethylenebis (indenyl) zirconium dichloride,
Ethylenebis (tetrahydroindenyl) zirconium dichloride,
Diphenylmethylene-9-fluorenylcyclopentadienylzirkoniumdichlorid,
Dimethylsilanediylbis (3-tert-butyl-5-methylcyclopentadienyl) zirconium dichloride,
Dimethylsilanediylbis (2-methylindenyl) zirconium dichloride,
Dimethylsilanediylbis (2-methylbenzindenyl) zirconium dichloride dimethylsilanediylbis (2-methyl-4-phenylindenyl) zirconium dichloride,
Dimethylsilanediylbis (2-methyl-4-naphthylindenyl) zirconium dichloride,
Dimethylsilanediylbis (2-methyl-4-isopropylindenyl) zirconium dichloride or
Dimethylsilanediylbis (2-methyl-4,6-diisopropylindenyl) zirconium dichloride and the corresponding dimethylzirconium compounds.

The metallocene compounds are either known or obtainable by methods known per se.

Furthermore, the metallocene catalyst systems contain metallocenium ion forming compounds. Suitable are strong, neutral Lewis acids, ionic compounds with Lewis-acid cations or ionic compounds with Bronsted acids as cation. Examples of these are tris (pentafluorophenyl) borane, tetrakis (pentafluorophenyl) borate or salts of N, N-dimethylanilinium. Also suitable as metallocenium ion-forming compounds are open-chain or cyclic alumoxane compounds. These are usually prepared by reaction of trialkylaluminum with water and are usually mixtures of different lengths, both linear and cyclic chain molecules.

In addition, the metallocene catalyst systems organometallic compounds of the metals of I., II. Or III. Main group of the Periodic Table include such as n-butyl lithium, n-butyl-n-octyl magnesium or tri-iso-butyl-aluminum, triethylaluminum or trimethylaluminum.

The process according to the invention can be used for the pre-activation of catalysts used in the polymerization of C ₂ -C ₂₀ olefins. The polymerization can be carried out in at least one, often also in two or even more successive reaction zones (reactor cascade) in the gas phase, in the liquid phase, in the slurry phase or else in the bulk phase. The reaction conditions can also be adjusted in the actual polymerization so that the respective monomers are present in two different phases, for example, partly in the liquid and partly in the gaseous state (condensed mode).

The usual reactors used for the polymerization of C ₂ -C ₂₀ olefins can be used. Suitable reactors include continuously operated horizontal or vertical stirred tanks, circulation reactors, loop reactors, stage reactors or fluidized bed reactors. The size of the reactors is not essential to the process of the invention. It depends on the output that is to be achieved in or in the individual reaction zones.

In particular fluidized bed reactors and horizontally or vertically stirred powder bed reactors are used as reactors. The reaction bed in the process according to the invention generally consists of the polymer of C ₂ -C ₂₀ olefins which is polymerized in the respective reactor.

In a particularly preferred embodiment of the process according to the invention, the polymerization is carried out in a reactor or in a cascade of reactors connected in series, in which the pulverulent reaction bed is kept in motion by a vertical stirrer, wherein so-called freely supporting helical stirrers are particularly well suited. Such stirrers are, inter alia, from EP-B 000 512 and the EP-B 031 417 known. They are characterized in particular by the fact that they distribute the powdery reaction bed very homogeneously. Examples of such powdery reaction beds are in the EP-B 038 478 described. Preferably, the reactor cascade consists of two kesselelförmigen connected in series, with a stirrer provided reactors with a volume of 0.1 to 100 m ³ , for example 12.5, 25, 50 or 75 m ³ .

According to the novel process for the pre-activation of catalysts for the polymerization of C ₂ -C ₂₀ olefins, the catalyst is first mixed with the respective monomer, then optionally the respective cocatalyst is added and the resulting mixture is then subjected to a preactivation in a tubular reactor. In the case of polymerization with the aid of Ziegler-Natta catalyst systems, this means that first the titanium-containing solid component a) is mixed with the respective monomer and then optionally added as cocatalysts organic aluminum compounds b) and electron donor c). In the case of metallocene catalysts, the complex compound of metals of subgroups of the Periodic Table with organic ligands is first mixed with the respective monomer and then, if appropriate, alumoxane compounds are added to the resulting mixture as cocatalysts. Of course, if a polymerization catalyst does not require a cocatalyst, the corresponding process step can also be omitted.

Subsequently, subjecting the mixture obtained in a tubular reactor preactivation, preferably at temperatures of -25 to 150 ° C, in particular from -15 to 100 ° C, pressures of 10 ⁵ to 10 ⁷ Pa (1 to 100 bar), in particular from 10 ⁶ to 6.10 ⁶ Pa (10 to 60 bar) and average residence times of the reaction mixture of 1 to 5 minutes, in particular from 1 to 3 minutes. It may also be advisable to carry out a prepolymerization of the entrained monomers by adding suitable cocatalysts in the tubular reactor.

The tube reactors used in the preactivation process according to the invention preferably have a length / diameter ratio of 50,000: 1 to 50: 1, in particular from 10,000: 1 to 100: 1. As tube reactors, the tube reactors customary in plastics technology can be used, for example endlessly welded V _2A steel tubes or weldable V _2A steel tube sections. In particular, in the case of very reactive catalysts, it may be advisable to use such a tubular reactor, which has a smooth, endless inlet tube without seams in the interior. Plastic, metal, graphite or ceramic, in particular Teflon or ceramic-doped Teflon, is suitable as the material for such an inlet tube. With such an inlet tube, it is possible inter alia to prevent the formation of deposits on the pipe wall. Furthermore, the tubular reactor can be provided at various points with a metering device, for example, in addition Feed monomers, catalysts, cocatalysts or additives.

In the process according to the invention, it is essential that the mixture of catalyst, optionally cocatalyst and monomer in the form of a turbulent plug flow having a Reynolds number of at least 2300, in particular of at least 5000, based on pure propylene, is passed through the tubular reactor and preactivated there the Reynolds number is a characteristic of the course of pipe flow, in which it defines the ratio of inertial to frictional forces in flowing liquids according to the following equation (III): $$\mathrm{RE}=\frac{2\mathrm{R}\cdot \mathrm{\nu }\cdot \mathrm{\zeta }}{\mathrm{\eta }}$$

R:

den Halbmesser des durchströmenden Rohres

ν:

die mittlere Strömungsgeschwindigkeit

ζ:

die Dichte der zu messenden Flüssigkeit sowie

η:

die dynamische Viskosität der zu messenden Flüssigkeit.

In the equation (III) mean

R:

the radius of the flowing pipe

ν:

the mean flow velocity

ζ:

the density of the liquid to be measured as well

η:

the dynamic viscosity of the liquid to be measured.

In order to avoid blockages in the tubular reactor, it may further be advisable to introduce the catalyst and, if appropriate, the cocatalyst via a suitable homogenization unit into the tubular reactor in order to ensure homogeneous catalyst concentration at all times and thus controlled heat removal during the preactivation. Suitable homogenization units include countercurrent nozzles, axial mixers, laminar flow mixers, static mixers and other common technical mixers. Depending on the catalyst used, the temperature of the monomer used and the corresponding gas mixture can also be varied. The homogenization unit can still be coated with an inlet of metal, plastic or ceramic to achieve a smooth surface in the interior, wherein plastic inlets are preferred. Furthermore, an upstream catalyst metering device can be used, inter alia, a metering device customary in the polymerization of olefins, for example a dimple feeder, a double-check feeder or metering pumps. Here, the catalyst may, inter alia, as a solid or as a suspension, for example in liquid monomer or in Hydrocarbons such as used in heptane or iso-dodecane.

The process according to the invention is then used to introduce the preactivated catalyst into the corresponding polymerization reactor, where the actual polymerization of the C ₂ -C ₂₀ -olefins takes place.

In the process of the invention, the actual polymerization under standard reaction conditions at temperatures of 40 to 150 ° C and pressures of 1 to 100 bar is made. Preference is given to temperatures of 40 to 120 ° C, in particular from 60 to 100 ° C and pressures of 10 ⁶ to 5.10 ⁶ Pa (10 to 50 bar), in particular from 20 to 40 bar. The molecular weight of the polymers of the C ₂ -C ₂₀ olefins formed can be controlled and adjusted by the addition of regulators customary in polymerization technology, for example hydrogen. In addition to regulators, so-called regulators, ie compounds which influence the catalyst activity, or antistatic agents can also be used. The latter prevent the formation of deposits on the reactor wall by electrostatic charging. The polymers of the C ₂ -C ₂₀ olefins generally have a melt flow rate (MFR) of 0.1 to 3000 g / 10 min., In particular from 0.2 to 100 g / 10 min, at 230 ° C and weighing 2.16 kg, on. The melt flow rate corresponds to the amount of polymer which is pressed within 10 minutes from the ISO 1133 standardized test apparatus at a temperature of 230 ° C and under a weight of 2.16 kg. Particular preference is given to those polymers whose melt flow rate is 5 to 50 g / 10 min, at 230 ° C and under a weight of 2.16 kg.

In the process according to the invention, the mean residence times in the actual polymerization of the C ₂ -C ₂₀ -olefins are in the range from 0.1 to 10 hours, preferably in the range from 0.2 to 5 hours and in particular in the range from 0.3 to 4 hours ,

According to one embodiment of the method according to the invention for the pre-activation of catalysts, it is also possible to carry out the metering of monomer, catalyst, optionally cocatalyst and auxiliary substances, for example hydrogen, both into the tubular reactor and additionally into the actual polymerization reactor. In this way it is possible to control the process in different places.

With the help of the method according to the invention for the pre-activation of catalysts for the polymerization of C ₂ -C ₂₀ olefins, it is possible, inter alia, the reactor stability, the space / time yield and the To improve the productivity of the polymerization processes. Furthermore, the polymerization of C ₂ -C ₂₀ olefins can be significantly better controlled by the extended dosing possibilities of monomers, catalyst, optionally cocatalyst and regulator. In addition, a reduction in the formation of scale and lumps in the polymerization reactor and a marked improvement in the morphology of the resulting polymers of C ₂ -C ₂₀ olefins due to reduction of the fine dust content and a narrower particle size distribution are observed. The resulting polymers of C ₂ -C ₂₀ olefins also show better product homogeneity. The inventive method is technically feasible cost-effectively and easily to be controlled without much effort.

The method according to the invention can be carried out in the following device. This consists i.a. from feed devices for metering in the catalyst, optionally the co-catalyst and the monomer, optionally an adjoining homogenizer, optionally another feed device for the cocatalyst and connected thereto, a tubular reactor whose discharge is connected to a polymerization reactor. The device can also be designed in such a way that the polymerization reactor further feeders for monomers, catalysts, optionally cocatalysts and auxiliaries are. Furthermore, a smooth endless inlet tube without seams can be contained in the tube reactor.

By means of the process according to the invention, various types of polymers of C ₂ -C ₂₀ olefins can be prepared, for example homopolymers, copolymers or mixtures of such polymers. These are particularly suitable for the production of films, fibers or moldings.

Examples

In the experiments of Examples 1, 2 and Comparative Example A, a Ziegler-Natta catalyst system was used which contained a titanium-containing solid component a) prepared by the following process.

In a first step, a finely divided silica gel having a mean particle diameter of 30 μm, a pore volume of 1.5 cm ³ / g and a specific surface area of 260 m ² / g was treated with a solution of n-butyloctylmagnesium in n-heptane offset, wherein per mole of SiO ₂ 0.3 mol of the magnesium compound were used. The finely divided silica gel was additionally characterized by a medium Particle size of the primary particles of 3-5 microns and characterized by cavities and channels with a diameter of 3-5 microns, wherein the macroscopic volume fraction of the cavities and channels on the total particle was about 15%. The solution was stirred for 45 minutes at 95 ° C, then cooled to 20 ° C, after which the 10-fold molar amount, based on the organomagnesium compound, of hydrogen chloride was introduced. After 60 minutes, the reaction product was added with constant stirring with 3 moles of ethanol per mole of magnesium. This mixture was stirred for 0.5 hours at 80 ° C and then treated with 7.2 mol of titanium tetrachloride and 0.5 mol of di-n-butyl, in each case based on 1 mol of magnesium. The mixture was then stirred for 1 hour at 100 ° C, the resulting solid filtered off and washed several times with ethylbenzene.

The resulting solid product was extracted for 3 hours at 125 ° C with a 10 vol .-% solution of titanium tetrachloride in ethylbenzene. Thereafter, the solid product was separated by filtration from the extractant and washed with n-heptane until the extractant had only 0.3 wt .-% titanium tetrachloride.

• 3,5 Gew.-% Ti
• 7 , 4 Gew.-% Mg
• 28,2 Gew. - % Cl.

The titanium-containing solid component a) contained

• 3.5% by weight of Ti
• 7, 4 wt .-% Mg
• 28.2% by weight of Cl.

In addition to the titanium-containing solid component a) as cocatalysts triethylaluminum and organic silane compounds analogous to the teaching of US Pat. No. 4,857,613 and the US Pat. No. 5,288,824 used.

example 1

The polymerization was carried out in a vertically mixed gas phase reactor with a useful volume of 200 l, equipped with a self-supporting helical stirrer (87 rpm). The reactor contained a moving solid bed of 45 kg of finely divided polymer. The reactor pressure was 32 bar. The catalyst used was the titanium-containing solid component a).

First, propylene was mixed as a monomer with the catalyst, ie, the titanium-containing solid component a). The metering of the catalyst was carried out at room temperature together with the fresh propylene added for pressure control. The metered amount of catalyst was such that the average output of 45 kg of polypropylene per hour was maintained. The catalyst / propylene mixture was metered in via a dimple feeder with lateral expansion, flash cyclone in the flue gas line and nitrogen flushed nitrogen. Subsequently, the catalyst / propylene suspension was transferred from above into a cylindrical vessel (a homogenizer) whose inside walls were polished (d _inside = 100 mm, 1 = 375 mm) by means of a flexible metering line (d _inside = 6 mm). After homogenization of the bagged Katalysatorschuß the propylene / catalyst mixture was continuously transferred to a pressure-stable tubular reactor with loose endless laid Teflon _tube (1 _{tube reactor} = 100 m, d _inside (teflon _tube ) = 6 mm). A mixture of triethylaluminum (in the form of a 1 molar heptane solution) in an amount of 135 mmol / h and 13.5 mmol / h of dicyclopentyldimethoxysilane (in the form of a 0.125 molar heptane solution) was metered into the gas phase reactor. Hydrogen was metered into the cycle gas cooler for the molecular weight control. The hydrogen concentration in the reaction gas was 3.3% by volume and was determined by gas chromatography. In the tube reactor, the mixture of catalyst and propylene at a temperature of 20 ° C, a pressure of 4.10 ⁶ Pa (40 bar) and a mean residence time of 1.6 minutes was briefly pre-activated and then rinsed into the gas phase reactor. In this case, the mixture of catalyst and propylene with a Reynolds number of 32,400, based on the propylene, flowed through the tubular reactor.

The pre-activated in this way catalyst was then transferred together with the propylene in the gas phase reactor and polymerized there.

The resulting in the polymerization in the gas phase reactor residual heat was removed by evaporation cooling. For this purpose, a circulating gas stream, which constitutes 4 to 6 times the amount of gas converted quantitatively, was circulated. The vaporized propylene was withdrawn after passing through the reaction zone at the top of the reactor, separated in a recycle gas filter of entrained polymer particles and condensed against secondary water in a heat exchanger. The condensed cycle gas was pumped back to 40 ° C back into the reactor. The hydrogen which was not condensable in the condenser was sucked off and returned to the liquid circulating gas stream from below. The temperature in the reactor was controlled by the cycle gas flow and was 80 ° C, the pressure 3.2.10 ⁶ Pa (32 bar).

By briefly depressurizing the reactor via a dip tube, successive polymer grits were removed from the reactor. The discharge frequency was controlled by a radiometric level measurement. This setting was stable for a total of 75 hours and then turned off in a controlled manner. This gave a propylene homopolymer with a melt flow rate (MFR), according to ISO 1133 of 12.2 g / 10 min.

The process parameters in the gas phase reactor and characteristic product properties of the polymer obtained are shown in Table I below.

Example 2

The polymerization in the continuously operated 200 l gas phase reactor was carried out analogously to Example 1. The catalyst was metered in analogously to Example 1. The mixture of triethylaluminum (in the form of a 1 molar haptan solution) in an amount of 135 mmol / h and 13.5 mmol / h of dicyclopentyldimethoxysilane (in the form of a 0.125 molar heptane solution) was injected by means of an injection ( d _inside = 2 mm) directly into the beginning of the tube reactor with Tefloninlet metered. Here, the amount of fresh polypropylene was divided so that 80% by mass of fresh propylene with the catalyst (titanium-containing solid component a)) and 20% by mass of fresh propylene with the heptane solutions of triethylaluminum and dicyclopentyldimethoxysilane were flushed into the tube reactor together. In the tube reactor, the mixture of catalyst, cocatalyst and propylene was passed with a Reynolds number of about 32400 in the direction of the tube end, while the prepolymer was prepolymerized. This setting was stable over a total of 75 hours and then turned off in a controlled manner. In the tubular reactor, the prepolymerization was carried out at a pressure of 4.10 ⁶ Pa (40 bar) and an average residence time of 1.6 minutes. The thus pre-activated catalyst was then transferred together with the already obtained propylene polymer and the unreacted propylene in the gas phase reactor and further polymerized there.

The process parameters in the gas phase reactor and characteristic product properties of the resulting polymer are listed in Table I below.

Comparative Example A

The polymerization in the continuously operated 200 l gas phase reactor was carried out analogously to Example 1. The catalyst / propylene mixture was metered laterally into the reactor via a dimple feeder with lateral expansion, cyclone in the flue gas line and nitrogen purge flushed. The dosage of Triethylaluminum and dicyclopenyldimethoxysilane occurred directly in the gas phase reactor.

In contrast to Example 1 was omitted in Comparative Example A on the short-term preactivation in the tubular reactor. The setting was stably driven for a total of 75 hours and then turned off in a controlled manner. The process parameters in the gas phase reactor and the characteristic product properties of the resulting polymer are listed in Table I below. Table I example 1 Example 2 Comparative Example A Reactor pressure 10 ^-5 Pa ([bar]) 32 32 32 Reactor temperature [° C] 80 80 80 Stirrer revolutions [rpm] 87 87 87 average residence time [min] tubular reactor 1.6 1.6 - Gas phase reactor 60 60 60 Hydrogen [% vol] 3.3 3.2 3.4 MFR [g / min] 12.2 12.3 12.3 Productivity [gPP / gKat] 16200 22700 15500 Polymer powder morphology <0.125 mm [%] 4.0 2.1 11.4 <0.25 mm [%] 8.4 2.1 11.1 <0.5 mm [%] 20.4 9.5 21.4 <1.0 mm [%] 46.7 36.1 32.8 <2.0 mm [%] 20.1 46.5 22.1 > 2.0 mm [%] 0.4 0.4 1.2

The melt flow rate (MFR) at 230 ° C and 2.16 kg according to ISO 1133 and the Polymergrießmorphologie was determined by sieve analysis. The productivity was calculated from the chlorine content of the resulting polymers according to the following formula: $$\mathrm{productivity}\left(\mathrm{P}\right)\mathrm{=}\mathrm{Cl}\mathrm{-}\mathrm{Content\; of\; the\; catalyst}\mathrm{/}\mathrm{Cl}\mathrm{-}\mathrm{Content\; of\; the\; polymer}$$

The obtained propylene homopolymers of Inventive Example 2 and Comparative Example A were further subjected to a melt filtration test.

In the melt filtration, the polymer melt at 265 ° C through a sieve with a mesh size of 5 microns and a surface of 434 mm ² by means of an extruder under pressure for 60 minutes pressed through, so that the throughput is 2 kg / h. The presence of unmelted particles and / or inorganic particles causes a constant increase in the measured melt pressure at a constant throughput. The results of melt filtration of the polymers of Example 2 and Comparative Example A are summarized in Table II. Table II Running time [min] Melt pressure 10 ^-5 Pa ([bar]) Example 2 Melt pressure 10 ^-5 Pa ([bar]) Comparative Example A 5 86 84 10 86 87 15 86 90 20 87 93 25 87 96 30 88 99 35 89 104 40 89 110 45 89 119 50 90 126 55 91 138 60 92 147

The results of the melt filtration tests show that the process according to the invention gives polymers which are more homogeneous than corresponding polymers which have been obtained by conventional processes.

• 0,98 kg (1,7 mol) rac. Dimethylsilylenbis(2-methylbenz[e]indenyl)zirkoniumdichlorid wurden in einem 300 1 Rührbehälter unter Stickstoff vorgelegt und bei Raumtemperatur unter Rühren in 124 kg 1,53 molarer (bezogen auf Al) MAO-Lösung (Fa. Witco; 10 Gew.-% Methylaluminoxan in Toluol) gelöst. Zwei Drittel der auf diese Weise erhaltenen Lösung wurden auf das im Prozeßfilter mit möglichst ebener Oberfläche vorgelegte, chemisch getrocknete Kieselgel innerhalb von 3 h aufgesprüht, wobei der Ablauf des Prozeßfilters geöffnet blieb. Das letzte Drittel der Lösung wurde nicht mehr aufgesprüht, sondern direkt von oben zu der überstehenden Lösung dosiert, ohne den vorgelegten Träger aufzuwirbeln. Nach vollständiger Zugabe der Lösung wurde,der Ablauf geschlossen. Am nächsten Tag wurde der Ablauf wieder geöffnet und die restliche Lösung zunächst drucklos, gegen Ende dann unter leichtem Stickstoffüberdruck, abfiltriert. Der zurückgebliebene Feststoff wurde nach Aufsprühen von 60 1 Pentan 1 h gerührt. Nach dem Abfiltrieren wurde noch zweimal mit je 60 1 Pentan gewaschen und der zurückgebliebene Trägerkatalysator dann im Stickstoffstrom getrocknet (2 h bei 35-40°C Innentemperatur und sehr langsamen Rühren). Die Ausbeute betrug 34,8 kg Metallocen-Trägerkatalysator.

In the experiments of Examples 3, 4 and the comparative example, a metallocene catalyst was prepared, which was prepared as follows:

• 0.98 kg (1.7 mol) of rac. Dimethylsilylenebis (2-methylbenz [e] indenyl) zirconium dichloride were placed under nitrogen in a stirred vessel at room temperature and stirred at room temperature with stirring in 124 kg of 1.53 molar (based on Al) MAO solution (Witco, 10% by weight). Methylaluminoxane in toluene). Two thirds of the solution obtained in this way were sprayed onto the chemically dried silica gel initially introduced in the process filter with as even a surface as possible within 3 h, the effluent the process filter remained open. The last third of the solution was no longer sprayed, but dosed directly from above to the supernatant solution, without whirling up the presented support. After complete addition of the solution, the drain was closed. The next day, the process was reopened and the remaining solution was first filtered off without pressure, towards the end then under slight nitrogen pressure. The remaining solid was stirred for 1 h after spraying 60 l of pentane. After filtering, the mixture was washed twice with 60 l of pentane and the remaining supported catalyst then dried in a stream of nitrogen (2 h at 35-40 ° C internal temperature and very slow stirring). The yield was 34.8 kg supported metallocene catalyst.

Example 3

The polymerization was carried out in a vertical mixed gas phase reactor with a useful volume of 200 l equipped with a self-supporting spiral stirrer (95 rpm). The reactor contained a moving fixed bed of 45 kg of finely divided polymer. The reactor pressure was 28 bar. As the catalyst, the metallocene catalyst described above was used. Such metallocene catalysts are already polymerization-active in the presence of monomer. The dosing of the catalyst was carried out as a suspension in iso-dodecane together with the fresh polypropylene added at -5 ° C. before pressure control. 20 mmol / h of isopropanol (in the form of a 0.5 molar heptane solution) were metered into the fresh propylene before the metered addition of catalyst. The metered amount of catalyst was such that the average output of 20 kg of polypropylene per hour was maintained. The catalyst / fresh propylene mixture was metered via a dimple feeder with lateral expansion, flash cyclone in the flue and nitrogen purge flushed. Subsequently, the catalyst / fresh propylene suspension was transferred from above into a cylindrical vessel whose inner walls were polished by means of a flexible metering line (D _in = 6 mm) (d _in = 100 mm, 1 = 375 mm). After homogenization of the bagged catalyst shot, the propylene / catalyst mixture was transferred continuously into a pressure-stable tubular reactor with loose endless laid Teflon _tube (1 _{tube reactor} = 50 m, d _inside (teflon _tube ) = 6 mm). In the gas phase reactor was added triisobutylaluminum (in the form of a 2 molar heptane solution) in an amount of 60 mmol / h.

In the tubular reactor, the propylene / catalyst mixture at a temperature of -5 ° C a pressure of 38x10 ⁵ Pa (38 bar) and a mean residence time of 1.5 minutes was rinsed in the gas phase reactor and prepolymerized. At this time, the mixture of catalyst flowed and propylene having a Reynolds number of about 17,500, based on the propylene, through the tubular reactor.

The thus pre-activated catalyst was then transferred together with the already obtained propylene polymer and the unreacted propylene in the gas phase reactor and further polymerized there.

The heat of reaction formed during the polymerization was removed by evaporative cooling. For this purpose, a circulating gas stream, which constitutes 4 to 6 times the amount of gas reacted quantitatively, was circulated. The vaporized propylene was withdrawn after passing through the reaction zone at the top of the reactor, separated in a recycle gas filter of entrained polymer particles and condensed against secondary water in a heat exchanger. The condensed cycle gas was pumped back into the reactor at 40 ° C. The temperature in the reactor was controlled by the cycle gas flow and was 70 ° C.

By briefly depressurizing the reactor via a dip tube, successive polymer grits were removed from the reactor. The discharge frequency was controlled by a radiometric fill level. This setting was stable over a total of 75 hours and then turned off in a controlled manner.

The process parameters in the gas phase reactor and the characteristic product properties of the resulting polymer are listed in Table III below.

Example 4

The polymerization in the continuous 200 l gas-phase reactor was carried out analogously to Example 3. The catalyst was metered in analogously to Example 3. Triisobutylaluminum (in the form of a 2 molar heptane solution) in an amount of 60 mmol / h was metered into the beginning of the tube reactor with Tefloninlet with the aid of an injection flush (d _inner = 2 mm). Here, the fresh propylene amount was divided so that 80 mass% of fresh propylene with the catalyst and 20 mass% of fresh propylene with the triisobutylaluminum heptane solution were purged together into the tube reactor.

This setting was stable over a total of 75 hours and then turned off in a controlled manner. The thus pre-activated catalyst was then used together with the already obtained propylene polymer and unreacted Propylene transferred to the gas phase reactor and further polymerized there.

The process parameters in the gas phase reactor and the characteristic product properties of the resulting polymer are listed in Table III below.

Comparative Example B

The polymerization in the continuous 200 l gas phase reactor was carried out analogously to Example 3 and Example 4. The catalyst / fresh propylene / iso-propanol mixture was metered laterally into the reactor via a dimple feeder with lateral expansion, cyclone in the waste gas line and nitrogen purge flushed. The dosage of triisobutylaluminum was carried out analogously to Example 3.

This setting was stable over a total of 75 hours and then turned off in a controlled manner. In contrast to Example 3, the pre-activation in the tubular reactor was omitted in Comparative Example B.

The procedural .Parameters and the characteristic product properties of the resulting polymer are listed in Table III below. Example 3 Example 4 Comparative Example B Reactor pressure 10 ^-5 Pa ([bar]) 28 28 28 Reactor temperature [° C] 70 70 70 Stirrer revolutions [rpm] 95 95 95 MFR [g / min] 7.4 7.2 8.4 Productivity [gPP / Cat] 7800 9100 6900 Polymer powder morphology: <0.125 mm [%] 0.1 0.2 0.3 <0.25 mm [%] 0.5 0.6 0.6 <0.5 mm [%] 4.6 8.0 3.6 <1.0 mm [%] 25.4 11.5 38.0 <2.0 mm [%] 64.1 76.8 48.4 > 2.0 mm [%] 5.3 2.9 9.1

The melt flow rate (MFR) at 230 ° C and 2.16 kg according to ISO 1133 and the Polymergrießmorphologie was determined by sieve analysis. The productivity was calculated from the chlorine content of the resulting polymers according to the following formula: $$\mathrm{productivity}\left(\mathrm{P}\right)\mathrm{=}\mathrm{Cl}\mathrm{-}\mathrm{Content\; of\; the\; catalyst}\mathrm{/}\mathrm{Cl}\mathrm{-}\mathrm{Content\; of\; the\; polymer}$$

Claims (10)

1. A process for the pre-activation of catalysts for the polymerisation of C₂-C₂₀ olefins, wherein the catalyst is initially mixed with the respective monomer, the respective co-catalyst, if necessary, is subsequently added, and the mixture thus obtained is subsequently subjected to a pre-activation in a tubular reactor and eventually the catalyst pre-activated in this way is introduced into the actual polymerisation reactor, characterised in that the mixture of catalyst, where necessary co-catalyst and monomer is conducted through the tubular reactor in the form of a turbulent plug flow with a Reynolds number of at least 2300.
2. The process according to claim 1, characterised in that the mixture of catalyst, where necessary co-catalyst and monomer is conducted in the form of a tubular plug stream with a Reynolds number of at least 5000 through the tubular reactor.
3. The process according to claim 1 or 2, characterised in that the tubular reactor used contains inside a smooth, endless, seamless inlet tube.
4. The process according to claims 1 to 3, characterised in that the mixture is conducted through the tubular reactor at temperatures of -25 to 150°C, pressures of 10⁵ to 10⁷ Pa (1 to 100 bar) and average residence times of 1 to 5 minutes.
5. The process according to claims 1 to 4, characterised in that the process is used for the production of homopolymers of propylene.
6. The process according to claims 1 to 5, characterised in that the process is used for the production of copolymers of propylene with other olefins with up to 10 C atoms.
7. The process according to claims 1 to 6, characterised in that the mixture of catalyst, monomer and co-catalyst is subjected to a pre-polymerisation in the tubular reactor.
8. The process according to claims 1 to 7, characterised in that the polymerisation of the C₂-C₂₀ olefins is carried out by means of a Ziegler-Natta catalyst which, apart from a titanium-containing solid component a) further comprises co-catalysts in the form of organic aluminium compounds b) and electron donor compounds c).
9. The process according to claims 1 to 8, characterised in that the polymerisation of the C₂-C₂₀ olefins is carried out by means of a Ziegler-Natta catalyst based on metallocene compounds or polymerisation-active metal complexes.
10. The process according to claims 1 to 9, characterised in that a vertical stirred powder bed reactor is used as the actual polymerisation reactor.